I'm unfamiliar with the contemporary technology in neurobiology. I'm interested in the possibilities to measure very small energy fluctuations in the brain, the location of the activities is rather unimportant for my purpose. I would be very grateful for any suggestions regarding the relevant literature.
Dear Mr Connelly,
I'm interested in non-invasive ways to measure brain activity. As far as I understand it, this means primarily to measure the electrical activity or the thereby induced electromagnetic fields. I have used “energy“ to refer to a property that must be transferred within the brain for the brain to do work. The reason why I have used the broader term “energy” instead of electrical activity is because if there are non-invasive ways to measure other forms, for example in chemical reactions, that would be interesting as well.
I'm interested in possibilities to observe activities caused by language use and associated cognitive processes. For theoretical reasons, I'm sceptical about what C. R. Gallistel and Adam Philip King have called “system-level structures (neural circuits)” and “cellular-level structures (e. g. synapses)”. They argue that one may look for the fundamental processes on a deeper level, what they call “molecular structures (e. g., microRNAs)”. Gallistel and King do not refer to language, but it seems to me that some of their arguments apply to language as well. Hence my question: How small is the smallest quantity of something that does work and that can be observed in brain (in the hope that the answer may give an indication about what “level” can be studied).
The cited phrases can be found on page 53f. in C. R. Gallistel and Adam Philip King, Memory and the Computational Brain, Blackwell 2007.
Sven Beecken
Well the smallest voltage you're going to be able to measure in a single trial is around a microvolt, so EEG. You might also want to look into "Magnetoencephalography", and fMRI. All optical measurements (of any resolution) require crainiotomies.
Dear Mr Connelly,
Thank you for your answer, it is very helpful. I will look into the technologies you suggested. Hypothetically speaking, could a smaller voltage be measured if a craniotomy is performed?
Best,
Sven Beecken
Smaller voltages, no. But you can genetically encode optical sensors (see GCaMP6) which will allow you an *almost* perfect read out neural activity (single cell resolution, 10s of millisecond time resolution).
Hello I am not an expert on that so pardon but it would seem to be on the order of one or a few photons depending on your theory and what fluctuations you speculate matter. Either you are looking for quantum level changes which you could capture with a total surround of the brain or a partial surround with compensatory assumptions, or you are looking for much more macroscopic change such as heat flow, where the resolution would of course be rather coarse particularly with probable difficulties arranging for a tightly controlled experiment.
Put another way, with less confidence you can make assumptions that make the test easier and at least reduce the hypothesis set thereby.
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